Gasket for parabolic ramp self restraining bell joint

ABSTRACT

Gaskets for use with a bell and spigot coupling system are disclosed herein. The gasket comprises an elastomeric member having a front edge, a first section, and a second section. Axial forces generated by the insertion of the spigot to the first section of the elastomeric member displace the first section of the elastomeric member in an axial and radial direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/955,692, filed on Jul. 31, 2013, which is a continuation of U.S.patent application Ser. No. 13/543,763, filed on Jul. 6, 2012, which isa continuation-in-part of U.S. patent application Ser. No. 13/216,523,filed on Aug. 24, 2011, which claims the benefit of U.S. ProvisionalApplication 61/376,450, filed on Aug. 24, 2010, all of which are herebyincorporated by reference herein in their entireties.

FIELD

The disclosure is directed to couplings and methods of coupling,particularly to bell and spigot couplings and methods.

DESCRIPTION OF RELATED ART

Members of the flow control industry, such as producers of pipelinecomponents for the transmission of water, gas, oil, or other fluids havefocused substantial attention on the problem of creating and maintainingconnections between adjacent lengths of pipe, or pipes and fittings, orpipes and valves. In applications where the fluid, such as water forfire mains or water distribution in municipalities, is under highpressure, various means are used to prevent separation of the jointsbetween piping components. Piping components are joined to preventseparation caused by thrust forces, earth movement, and externalmechanical forces exerted on piping components. These componentsinclude, for example, pipes, couplings, fittings, valves, and firehydrants. The majority of the solutions can be categorized into either“push-on joints,” “mechanical joints,” or “flanged joints.”

Iron pipe has traditionally been used to withstand the large pressuresthat are necessary for municipal water systems and other systems. Thosepressures are needed to carry fluids over long distances, to carry largeamounts of fluids, and to prevent contamination of the systems in theevent of a hole or other breach of the system. There are two relatedproblems in the history of using pipes of any sort, including iron pipe:(1) creating a secure seal to join the pipes and to withstand largepressures, and (2) bending or deflecting the joints of the pipes to meetthe intended use of the pipes.

The first substantial use of cast iron pipe was in Europe in the 17thcentury. The piping systems of the 17th and 18th centuries primarily hadflanged ends that bolted together with lead or rawhide gaskets forsealing. Flanged joints continue to be used for some applications today,but with rubber gaskets. Flanged joint systems are costly to install andrequire considerable maintenance.

The first bell and spigot joint was developed by Thomas Simpson of theChelsea Water Company in England in 1785. The joint was caulked withjute rope impregnated with pine resin or tallow and sealed in place withmolten lead. The bell and spigot joint remained the predominant pipejoint until the advent of the push-on joint, for example the TYTON®Joint, in 1956.

There are numerous methods of securing piping components in series tomake up a pipeline, roughly divisible into three main categories: (1)rigid, as with bolted flange connections; (2) flexible, as with numerousdesigns such as TYTON® push-on joints and gaskets, or TYTON® combinedwith self-restraining gaskets bearing toothed inserts, such as FIELD LOK350® Gaskets providing both sealing and autonomous restraint; and (3)others with a limited amount of incidental flexibility, such as PVC Pipewith Rieber Gaskets where minor flexibility is possible due to theplasticity of the gasket and pipe materials and to joint tolerancing.

Push-on solutions are exemplified by U.S. Pat. No. 2,953,398, andaccount for the majority of straight-run pipe connections. In a typicalconfiguration, a spigot of a pipe slides into a bell of another pipepast a tightly-fitted gasket. A variation of the push-on joint isevidenced by U.S. Pat. No. 2,201,372, which employs a compressionsnap-ring fitted within a special lip of the bell, in order to exertpressure onto locking segments and thus drive them into the spigot,restraining the joint against thrust forces. U.S. Pat. No. 3,445,120,likewise employs a gasket with toothed, locking segments encased thereinthat are generally disposed such that they and the gasket may rollbetween a locked and a free position. As the gasket rolls underextraction forces, it is intended eventually to encounter a position inwhich the segments must compress the gasket to allow further rotation ofthe segment and engagement of the teeth with the mating pipe spigot,thereby terminating the rotation and compression of the gasket andrestraining the joint.

Other examples of restrained push-on joints include those disclosed inU.S. Pat. Nos. 5,295,697, 5,464,228, and 5,067,751. In those references,the connection is effected by either locking segments or wedges withinthe gasket that engage the spigot. The locking segments possess a groovethat mates with an annular rib on the bell, such that the rib acts as arocker, or cam, or, alternatively, as a wedge. During insertion of thespigot into the bell, the segments rotate on the rib, but are preventedfrom appreciable axial movement by the mating of the rib and groove.Upon experiencing counter-forces tending to effect removal of thespigot, the rib acts as a cam, both causing the segments to pivot on therib as an axis, and exerting a radially inward pressure as the segmentattempts to slide past the rib. These types of joints depend oncompressive force on the rubber gasket to maintain the connection of thepipes.

While the push-on type joint has obtained wide acceptance for pipejoints, acceptance for fittings, valves, and hydrants is much lower. Thecontours of bell sockets of the push-on joint require a high degree ofprecision for a cast surface. In restrained joints, an additionallocking joint is necessary, which also requires a high degree ofprecision to manufacture. It often takes a high degree of skill andalignment precision, as well as substantial force (i.e. in the range of600 to 800 pounds of force for an eight inch size pipe), to assemblejoints using the above described push-on type joints. The insertionforce with present push-on designs increases proportionally with conduitdiameter. Moreover, insertion forces increase substantially inlow-temperature conditions.

A current trend in the industry is to manufacture pipe with walls muchthinner than the current designs. Whether the pipe end is produced in amanufacturing plant or is the result of field cuts required to adjustthe length of the pipe, it is not practical to have beveled or roundedends in such pipes. Damage to the gaskets or displacement of the gasketsis a likely outcome when inserting a spigot end of a pipe not properlyaligned or without a beveled or rounded end into the bell of anotherpush-on joint pipeline component. A further consequence of the highassembly forces required is that installers favor mechanical jointconnections for fittings, valves, and hydrant shoes because they requirelower assembly forces.

Attempts to design low insertion-resistance joints have been made in thepast using normal straight-sided conical bell sockets and straight-sidedconical gaskets, but these designs were not completely satisfactorybecause normal conical inner surfaces do not allow for sufficientdeflection of the bell and socket joint. During off axis rotation, atleast some of the locking segments of the gasket will be unable toengage the spigot due to misalignment in interface between the outersurface of the gasket and the inner surface of the bell socket. Thismisalignment can cause irregular engagement of the spigot, inconsistentloading of the gasket, point loads in the bell socket, unlocking oflocking segments, and/or broken teeth of the locking segments. Forexample, U.S. Pat. No. 3,815,940 and U.S. Patent Application PublicationNo. 2009/0060635 both show bells with conical inner surfaces. Thus thereis a need for a connection that is less sensitive to misalignment andtemperature extremes and has little to minimal frictional resistance tothe insertion of the spigot until the desired connection is achieved andthe coupling is maintained, yet maintains a seal under high pressures,even when the joint is deflected.

SUMMARY

The present disclosure overcomes the problems and disadvantagesassociated with current strategies and designs and provides new devicesand methods for connecting bell and spigot pipeline components.

An embodiment of the disclosure is directed to a conduit that comprisesat least one bell with an end face, an internal portion, and a concaveinner surface between the end face and the internal portion. Thediameter of the inner surface adjacent to the internal portion isgreater than the diameter of the inner surface adjacent to the end face.

In preferred embodiments, the inner surface is a truncated ellipticparaboloid. In preferred embodiments, the conduit has a bell at a firstend and a spigot at a second end. Preferably, the conduit is cylindricaland is made of at least one of ferrous metals (e.g., steel and castiron, among others), non-ferrous metals, copper-based alloys, or plastic(e.g. PVC or HDPE).

Another embodiment of the disclosure is also directed to a conduit thatincludes multiple openings wherein at least one opening has a bell thatcouples to another piping component having a spigot. In preferredembodiments, the inner surface of the bell is concave. The inner surfaceis preferably a truncated elliptic paraboloid. In preferred embodiments,the conduit has a bell at a first end and a spigot at a second end.Preferably, the conduit is cylindrical and is made of at least one offerrous metals (e.g., steel and cast iron), non-ferrous metals,copper-based alloys, or plastic (e.g. PVC or HDPE).

Another embodiment of the disclosure is directed to a sealing device.The sealing device comprises at least one segment having a convex outersurface, and a K-type gasket coupled to the segment. In the preferredembodiments, the segment is a locking segment. The locking segmentfunctions as a restraining device and an anti-extrusion device toprevent the joint from separating and the elastomeric seal from beingextruded out of the joint when subjected to high internal hydraulicforces. In other embodiments, a guide segment without teeth issubstituted for the locking segment and serves as an anti-extrusiondevice for the polymeric material of the sealing portion.

In preferred embodiments, the segment is of a first material and theK-type gasket is of a second material. In preferred embodiments, theK-type gasket is comprised of a coupling section and a sealing section.The sealing section is preferably comprised of an upper section and alower section, each extending from the coupling section. The couplingsection, in preferred embodiments, has one or more expansion orcontraction grooves in the outer or inner periphery.

The locking segment, in preferred embodiments, has at least oneengagement device. Preferably, the device is annular.

Another embodiment of the disclosure is directed to a conduit couplingsystem. The system comprises at least two piping components and asealing device. A first component has a bell and a second component hasa spigot, the spigot is adapted to mate with the bell. The bell includesa first end and a second end, wherein the first end is coupled to thefirst component. The bell socket has a concave annular inner surface anda diameter of the annular inner surface adjacent to the first end of thebell socket is greater than a diameter of the annular inner surfaceadjacent to the second end of the bell socket. The sealing deviceincludes a segment comprising a convex outer surface and a K-type gasketcoupled to the segment. The sealing device is adapted to fit between thebell socket and the spigot end.

In preferred embodiments, the segment is a locking segment. Each lockingsegment is adapted to engage an outer surface of the spigot. The innersurface of the bell socket is preferably a truncated ellipticparaboloid. Each component preferably comprises a bell at a first endand a spigot or bell at a second end and each component is cylindrical.Each component can be made of ferrous metals (e.g., steel and castiron), non-ferrous metals, copper-based alloys, or plastic (e.g. PVC orHDPE).

In preferred embodiments, the locking segment is of a first material andthe K-type gasket is of a second material. Preferably, the firstmaterial is harder than the material of the spigot. In preferredembodiments, the K-type gasket has a coupling section and a sealingsection. The sealing section is preferably comprised of an upper sectionand a lower section, each extending from the coupling section.Preferably the locking segment has at least one engagement device. Inpreferred embodiments, the sealing device is annular.

Another embodiment of the disclosure is a method of coupling at leasttwo conduits. The method includes the steps of positioning a sealingdevice inside a bell coupled to one end of a first conduit, inserting aspigot of a second conduit through the sealing device inside the bell,and partially removing the spigot from the bell. A locking segment ofthe sealing device engages the outer surface of the spigot as the spigotis partially removed from the bell. The sealing device is adapted tomove axially within the bell in the direction of the insertion of thespigot and the movement is assisted by the presence of expansion andcontraction grooves in the coupling section of the gasket. This movementallows the locking segment to be displaced from the path of the incomingspigot with little increase in insertion force. The axial movement maybe confined to one segment of the sealing device to accommodate angularand radial misalignment of the incoming spigot. The sealing device isadapted to move in the direction of the partially removed spigot fromthe bell in response to internal hydraulic pressure to effect a seal tothe spigot that rests in an angular and radial misaligned position.

In preferred embodiments, the bell has a first end and a second end. Thefirst end is coupled to the first conduit. The bell has a concaveannular inner surface, and a diameter of the annular inner surfaceadjacent to the first end of the bell socket is greater than a diameterof the annular inner surface adjacent to the second end of the bellsocket.

In certain embodiments, radial loading of the locking segment increasesas the spigot is removed from the bell. The radial loading of thelocking segment can increase exponentially as the segment moves towardthe front of the bell following the parabolic curve toward the vertex.Preferably, the sealing device includes at least one locking segmentcomprising a convex outer surface, and a K-type gasket coupled to thelocking segment. Preferably the K-type gasket is compressed uponinsertion of the spigot. The withdrawal of the spigot end can be due toexternal forces or internal hydraulic forces.

Other embodiments and advantages are set forth in part in thedescription, which follows, and in part, may be obvious from thisdescription, or may be learned from practice.

DESCRIPTION OF THE DRAWINGS

The features and components of the following figures are illustrated toemphasize the general principles of the present disclosure and are notnecessarily drawn to scale. Corresponding features and componentsthroughout the figures may be designated by matching referencecharacters for the sake of consistency and clarity.

FIG. 1 is a partial cross-sectional view of an embodiment of a system inaccord with one embodiment of the current disclosure.

FIG. 2 is a partial cross-sectional view of an embodiment of a bell ofthe system of FIG. 1.

FIG. 3 is a partial cross-sectional view of an embodiment of a gasket ofthe system of FIG. 1.

FIG. 4 is a partial cross-sectional view of an embodiment of a lockingsegment of the system of FIG. 1.

FIG. 5 is a partial cross-sectional view of an embodiment of ananti-extrusion segment of the system of FIG. 1.

FIG. 6 is a partial cross-sectional view of an embodiment of the systemof FIG. 1 with the spigot prior to insertion into the bell.

FIG. 7 is a partial cross-sectional view of an embodiment of the systemof FIG. 1 with the spigot inserted into the bell.

FIG. 8 is a partial cross-sectional view of an embodiment of the systemof FIG. 1 with the gasket compressed more on the upper side due todeflection of the spigot.

FIG. 9 is a partial cross-sectional view of an embodiment of the systemof FIG. 1 with the locking segment engaged.

FIG. 10 is a cross-sectional view of an embodiment of the system of FIG.1 with the spigot deflected within the bell.

FIG. 11 is a picture of an experimental engagement pattern.

FIG. 12 is a picture of an experimental engagement pattern.

FIG. 13 is a picture of an experimental engagement pattern.

FIG. 14 is a perspective view a gasket in accord with one embodiment ofthe current disclosure.

FIG. 15 is a blow-out view of a bell, spigot, and gasket in accord withone embodiment of the current disclosure.

FIG. 16 is a cross-sectional view of a gasket in accord with oneembodiment of the current disclosure.

FIG. 17 is a partial cross-sectional view of a bell in accord with oneembodiment of the current disclosure.

FIG. 18 is a partial front view of an embodiment of a locking segment inaccord with one embodiment of the current disclosure.

FIG. 19 is a cross-sectional view of an anti-extrusion segment in accordwith one embodiment of the current disclosure.

FIG. 20 is an exploded cross-sectional view of an embodiment of ananti-extrusion segment in accord with one embodiment of the currentdisclosure.

FIG. 21 is a partial cross-sectional view of an embodiment of the systemin accord with one embodiment of the current disclosure.

FIG. 22 is a detail view of a lip of a bell of the system as denoted bydetail A of FIG. 21.

FIG. 23 is a cross-sectional view of a gasket in accord with oneembodiment of the current disclosure.

DETAILED DESCRIPTION

As embodied and broadly described herein, the disclosures herein providedetailed embodiments of the disclosed system, device, and method.However, the disclosed embodiments are merely examples that may beembodied in various and alternative forms. Therefore, there is no intentthat specific structural and functional details should be limiting, butrather the intention is that they provide a basis for the claims and asa representative basis for teaching one skilled in the art to variouslyemploy the principles of the present disclosure.

A problem in the art capable of being solved by the disclosedembodiments is coupling piping components and maintaining the assembly.It has surprisingly been discovered that certain configurations of theinterior surface of a bell socket increase ease of assembly and allowfor deflection between components. Furthermore, it has surprisingly beendiscovered that certain configurations of the outer surface of a gasketincrease the gasket's ability to maintain assembly during use of thecomponents including under high pressure applications.

FIG. 1 depicts a cutaway view of the components of the upper segment ofsystem 100. System 100 includes a spigot 105, a bell 110, and a sealingdevice 115. Each of spigot 105, bell 110, and sealing device 115 isshown in partial cross-section. In the preferred embodiment, each ofspigot 105, bell 110, and sealing device 115 is annular in shape havinga common axis below FIG. 1. Each of spigot 105, bell 110, and sealingdevice 115 can have any diameter that may be commonly found in pipingsystems. Preferably the diameter of each of spigot 105, bell 110, andsealing device 115 is between one-half inch and one hundred and twentyinches, more preferably between one-half inch and seventy two inches.

In a preferred embodiment, system 100 is used to join lengths of pipes.The pipes can be of any length. Additionally, one pipe can have onespigot end and one bell end, two spigot ends, two bell ends, or acombination thereof. In other embodiments, there can be at least onespigot and/or bell located along the length of the pipe positionedperpendicularly or at an angle to the axis of the pipe. In otherembodiments, system 100 can be used to join two or more pipes to othercomponents (e.g. fire hydrants, valves, and/or fittings), or can be usedto join components together. System 100 can be used for any fluid,including gas, water, or oil, for example. In the preferred embodiment,sealing device 115 has a gasket end 120 and a locking segment 125.However, in certain embodiments, segment 125 can be an anti-extrusionelement.

In the preferred embodiment, spigot 105 is made of ductile iron, steel,or plastic and segments 125 are made of gray iron, ductile iron, steel,or hardened plastic. However other material may be used, preferably butnot limited to ferrous metals (e.g. steel and cast-iron), non-ferrousmaterials, copper based alloys, or plastic (e.g. PVC or HDPE). Pipes canhave walls of any thickness, preferably, but not limited to, between ⅛inch and 1¼ inches. Fittings can have walls of any thickness,preferably, but not limited to, between ¼ inch and 2 inches.

In the preferred embodiment, sealing device 115 is of a diameter largerthan spigot 105 and has an annulus at the back with a diameter slightlysmaller than the diameter of spigot 105. The sealing device 115 ispreferably dimensioned such that spigot 105 can be inserted into sealingdevice 115 without encountering intentional resistance until such timeas it reaches the inner end of bell 110. Insertion forces are reduced byseveral orders of magnitude compared to compression type seals. Ifresistance is encountered during insertion as between the spigot 105 anda locking segment 125, the plasticity of the gasket, assisted by acompression groove 330 (shown in FIG. 3), the segment 125 is able toreduce the resistance by moving up and away from contact with the spigot105.

FIG. 2 depicts a cut away view of the upper segment of bell 110. Bell110 is preferably a push-on style bell. Bell 110 includes an outerdiameter 205, a bell chime 210 (to which the pipe or other component iscoupled), a bell face 215 at the open end of bell 110, and a bell socket220 (through which spigot 105 enters bell 110). In the preferredembodiment, bell 110 and the piping component is one unit, however inother embodiments, bell 110 can be coupled to the piping component byany other method known in the art, including, but not limited to,threading and screwing, welding, adhesive, fastening devices, andfriction fitting. Bell 110 preferably has an outer diameter larger thanthe outer diameter of the piping component, however in other embodimentsbell 110 can have an outer diameter equal to or smaller than the outerdiameter of the piping component.

Bell face 215 is coupled to bell socket 220 by bell throat 225. Theradius 230 between bell face 215 and bell socket 220 can have anydiameter. Preferably, radius 230 is adapted to facilitate insertion ofspigot 105 into bell 110. In the preferred embodiment, bell socket 220has an annular inner surface 235 starting at bell throat 225 and endingat gasket heel seat 239 into which sealing device 115 fits. In thepreferred embodiment, inner surface 235 is concave and has a diameteradjacent to gasket heal seat 239 that is greater than a diameter ofinner surface 235 adjacent to bell throat 225. However, in otherembodiments the diameter at bell throat 225 may be equal to or smallerthan the diameter gasket heel seat 239. Preferably, the decrease indiameter from gasket heal seat 239 to bell throat 225 is at a rapidlyincreasing rate. The cross-section of inner surface 235 can have anyshape, including but not limited to a truncated cone, a truncatedelliptic paraboloid, a truncated sphere, or a combination thereof.Paraboloids are surfaces generated by rotating a parabola about itscentral axis. Preferably, the curve of inner surface 235 has a nose or“vertex” of a paraboloid aligned in an axial direction opening away fromthe “directrix” of the paraboloid.

Gasket heel seat 239 and socket shoulder 245 mate with and retainsealing device 115 (described herein). In the preferred embodiment,adjacent to socket shoulder 245 is clearance slope 250. Clearance slope250 provides clearance for lip seal 335 (shown in FIG. 3) to move out ofthe way of an inserted spigot, and permits passage of the water or otherfluid into a pressure annulus groove 340 of sealing device 115 (shown inFIG. 3). In the preferred embodiment, the inner portion of bell socket220 is land 255, which extends from clearance slope 250 to land stop260. Land 255 provides clearance for spigot 105 and limitsoverdeflection of the joint. Land stop 260 limits the insertion depth ofspigot 105, while land radius 265 assists in casting by eliminating asharp inner corner between land 255 and land stop 260.

FIG. 3 depicts a cut away view of the upper segment of gasket 120 ofsealing device 115. Gasket 120 is preferably made of an elastomer.However, other materials that are flexible, appropriate for the fluid,and provide a tight seal can be used. For example, gasket 120 can bemade of SBR (Styrene butadiene rubber), EPDM (ethylene propylene dienemonomer rubber), Nitrile, NBR (Nitrile butadiene rubber), and/or othersynthetic and natural rubbers. In the preferred embodiment, gasket 120is of a single durometer rubber. However, in other embodiments, two ormore durometer rubbers can be used. Gasket 120 is preferably a K-type,lip, or wiper seal design, conforming to and fitting within the bell110. Gasket heel 305 and gasket shoulder 310 mate with gasket heel seat239 and socket shoulder 245 (as described with respect to FIG. 2). Inthe preferred embodiment, gasket heel 305 is slightly larger than gasketheel seat 239, thereby compressing gasket heel 305 so that it is firmlyanchored in bell socket 220 with gasket shoulder 310 against socketshoulder 245. Due to this configuration, gasket 120 is anchored withinbell 110 at the inner portion of the joint, away from throat 225,thereby allowing gasket 120 to move inward during insertion of spigot105.

Front edge slope 315 is the surface to which the locking segment oranti-extrusion segment is coupled. In the event that the edge of spigot105 contacts the segment 125, in the preferred embodiment, front edgeslope 315 is angled such that segment 125 and gasket 120 will bedeflected outward and away from spigot 105, allowing the passage ofspigot 105 through gasket orifice 320. The primary translation slope 325assists in stabilizing the front portion of gasket 120 and transferringforces to the expansion and contraction groove 330, which will bendand/or buckle to assist in the movement out of the path of an insertedspigot 105 until spigot 105 comes into contact with the front edge oflip seal 335. In the preferred embodiment, expansion and contractiongroove 330 is an annular cutout along the outer surface of gasket 120.However, in other embodiments, expansion and contraction groove 330 canbe located on the inner surface of gasket 120. In other embodiments,there can be multiple expansion and contraction grooves located atvarious locations about gasket 120. Furthermore, expansion andcontraction groove 330 can have any cross-sectional shape, including butnot limited to triangular, rectangular, trapezoidal, and semicircular.The back edge of gasket 120 contains a circumferential groove orpressure annulus pocket 340. Hydraulic pressure against pressure annulusgroove 340 increases the sealing pressure of lip seal 335 against themating spigot 105.

FIG. 4 depicts a cutaway view of the upper segment of segment 125, wheresegment 125 a is a locking segment. Segment 125 is preferably made ofAISI type 4140 steel (chromium steel). However other hard and durablematerials can be used, for example AISI type 431 stainless steel. Inpreferred embodiments, segment 125 may be coated with an anticorrosioncoating. The outer surface 405 of locking segment 125 a is preferably acurved surface that makes contact with the concave inner surface 235 ofbell socket 220. In the preferred embodiment outer surface 405 isconvex, more preferably a truncated paraboloid. However, in otherembodiments, outer surface 405 can be another convex surface, a linearsurface, or a concave surface. Preferably outer surface 405 opens awayfrom bell throat 225. Movement of outer surface 405 against the innersurface 235 of bell socket 220 facilitates locking segment 125 a inwedging between bell socket 220 and spigot 105, forcing the teeth 410 oflocking segment 125 a into the outer surface of spigot 105 and providingrestraint against extraction of spigot 105. While locking segment 125 ais shown with two teeth 410, one or more teeth can be used. For thinwalled spigots or PVC spigots, there should be more, shallower teeth 410located closer together than in embodiments using thick wall ironspigots. Additionally, in the preferred embodiment, for thin walledspigots or PVC spigots, there should be more segments located closertogether than in embodiments using thick wall iron spigots.

Due to the elasticity of the gasket 115 (being elastomeric), lockingsegments 125 a have freedom to move to maintain contact between outersurface 405 and the inner surface 235 of bell socket 220. Thus, segment405 can accommodate misalignments between the two surfaces caused by,for example, casting variability in the bell 110, as well as adifferential caused by the elliptical path of the locking segments 125 aduring deflection not matching exactly to inner surface 235.

Another function of locking segments 125 a is to assist in moving gasket120 away from spigot 105 as spigot 105 is inserted into bell 110.Segment mounting slope 415 is angled such that the corresponding matingfront end slope 315 of gasket 120 will help deflect gasket 120 up andaway from the path of spigot 105 so that passage is not impeded. Lockingsegment 125 a is aided by primary translation slope 325 of gasket 120,which supports the portion of gasket 120 forward of expansion andcontraction groove 330.

In the preferred embodiment, segments 125 are equally spaced and mountedto front end slope 315 of gasket 120. Segments 125 reinforce the elasticgasket material against extrusion between throat 225 and spigot 105. Inorder for segment teeth 410 to penetrate spigot 105, it is preferablefor locking segment 125 a to be made of a material harder than spigot105.

FIG. 5 depicts a cutaway view of the upper segment of segment 125, wheresegment 125 b is an anti-extrusion segment for non-restraining jointgaskets. In embodiments where restraint between a mating bell 110 andspigot 105 is not desired or needed, segment 125 b can be made withoutteeth as shown in FIG. 5. The toothless segment 125 b functionssimilarly to the locking segment 125 a in helping gasket 120 tofacilitate deflection and preventing extrusion of gasket 120 betweenthroat 225 of bell socket 220 and spigot 120, but has no teeth topenetrate spigot 105 and provide restraint. In some embodiments, bothlocking segments 125 a and toothless segments 125 b can be used in thesame restraining device 115. As shown in FIG. 23, in some embodiments,non-restraining segments such as segment 125 b may be replaced by anextended gasket 2300, wherein a bulb-shaped portion 2310 of the extendedgasket 2300 extends into the space normally occupied by segments 125,although the portion is typically annular and not segmented. Typically,such portion approximates the size and shape of segment 125 but is madeof gasket material. In such embodiments, greater deflection may be seen,as there is no metallic segment 125 to provide resistance to deflection.Additionally, the portion 2310 provides an additional sealing surface,as the portion 2310 extending is typically annular. Also, a visualdistinction between segmented restraining bell joints and the extendedgasket bell joints make it easier for field workers to identify thedifferent joints by visual inspection. Finally, the extended gasket belljoints do not require the inclusion of segments, which reduces materialcosts and tooling costs.

FIG. 6-9 depict cutaway views of the steps of inserting spigot 105through sealing device 115 and into bell 110. In FIG. 6, spigot 105 isaligned with bell 110. In the preferred embodiment, the centerline ofspigot 105 is aligned with the center line of bell 110. However, inother embodiments, spigot 105 can be inserted into bell 110 at an angle.The angle can be less than 15°. Preferably, the angle is less than 10°.Upon contact and continued insertion of spigot 105 (as shown in FIG. 7),lip seal 335 will stretch over spigot 105 imparting axial andcircumferential tensile forces to gasket 120, causing the activation ofsecondary translation slope 345 in bringing segments 125 into contactwith spigot 105.

In 8 inch pipe, for example, preferably, less than 100 pounds of forceare used to insert the spigot 105 into the bell 110, more preferablyless than 50 pounds of force are used, and even more preferably lessthan 25 pounds of force are used. In the preferred embodiment, theinsertion can be completed manually, without the use of mechanicaldevices other than to lift the piping component. Insertion of spigot 105through sealing device 115 will result in spigot 105 contacting lockingsegment 125. The geometries of the concave inner surface 235 and outersurface 405 of segment 125 aided by material characteristics of gasket120 and the expansion and contraction groove 330 in gasket 120 allow andguide the translation of segment 125 out of the way of incoming spigot105 with a minimum force. The translation vector is a combination ofaxial and radial movement in response to the orientation of the incomingspigot 105 and dimensional variations of the joint components. Thetranslation can include off-axis rotation of segment 125 in response tospigot 105 being deflected or offset. The energy stored in gasket 120 asa result of the translation keeps segment 125 in contact with spigot105. Insertion of spigot 105 through sealing device 115 induces axialtensile forces in sealing device 115, or at least positions segment 125to better engage spigot 105 when there is a withdrawal of spigot 105from bell 110 (as shown in FIG. 8). The circumferential tensile forcesexerted on lip seal 335 form a seal between lip seal 335 and spigot 105.The seal is amplified when the joint is pressurized and the material ofgasket 120 causes the seal to be pressed more tightly against spigot 105and the inner surface of bell 110 (as shown in FIG. 8). Gasket 120 canmove independently of segment 125 once segment 125 is seated.Furthermore, since, in the preferred embodiment, bell 110 is shaped suchthat the diameter decreases at an increasing rate from gasket heel seat239 to bell throat 225, the cavity between bell 110 and spigot 105allows gasket 120 to deform and move while the joint is pressurized,thereby aiding in preventing the gasket from blowing out of the joint.Spigot 105 does not have to be fully inserted into bell 110 to seal. Inthe preferred embodiment, spigot 105 will be sealed once the insertedend of spigot 105 is inserted past lip seal 335.

As shown in FIG. 9, retracting spigot 105 from bell 110, either fromexternal forces or by internal pressure in the pipeline, causes theteeth 410 to engage spigot 105 due to radial loading caused by theoutside surface of the segments bearing against the progressivelydecreasing curved inner surface 235 of bell 110 and forces teeth 410into spigot 105. Since, in the preferred embodiment, bell 110 is shapedsuch that the diameter decreases at an increasing rate from gasket heelseat 239 to bell throat 225, withdrawal of the spigot is met withincreasing resistance as the similarly formed outer surface 405 ofsegments 125 is wedged between the bell 110 and the mating spigot 105.The flexibility that allows segment 125 to translate out of the path ofthe incoming spigot 105 also allows segment 125 to rotate into anoff-axis position to maximize the engagement of teeth 410 with amisaligned or radially offset spigot 110 and to reduce the possibilityof point-loading conditions. In the preferred embodiment, segments 125are able to rotate within the confines of the bell 110 and spigot 105and settle in a position that minimizes stress.

When the joint is extended (pulled apart), the outer surface 405 oflocking segment 125 mates with the inner surface 235 of bell socket 220and forces teeth 410 into the outer surface of spigot 105 due to theparabolic wedging action of the outer surface of locking segment 125being drawn in the direction of its vertex. Withdrawal of spigot 105,either due to external forces or the internal hydraulic action caused bypressurizing the joint, causes teeth 410 to engage spigot 105 and theconvex outer surface 405 of locking segment 125 to engage thecorresponding concave inner surface 235 of bell socket 220. As thewithdrawal motion is continued, the engagement between the outer surface405 of locking segment 125 and inner surface 235 is intensified by theincreasingly smaller diameter of bell socket 220. This increases theinward radial loading on teeth 410, forcing them further to engagespigot 105. Extension of the joint is minimized due to the outer surfaceof locking segment 125 encountering an exponentially decreasing diameterof the inner surface 235 during pull-back, which exponentially increasesthe rate of radial loading of teeth 410 engaging spigot 105. Inembodiments where there are multiple locking segments 125, theengagement pressure on the outer surface of locking segments 125 wouldbe relatively equal since bell 110 and spigot 105 are in the form ofconcentric circles when axially aligned.

FIG. 10 depicts a cross-sectional view of a spigot 1005 coupled to abell 1010 deflected at an angle θ. The outer surface of segment 1025facilitates a deflection, or bending, of the joint between spigot 1005and bell 1010 by moving along inner surface 1020 of bell 1010. If θ isdefined as the angle of deflection as measured from the centerline CL ofthe bell 1010 and spigot 1005 components, then in the direction ofdeflection, segment 1025 will move along curve 1020 in the direction ofthe vertex, or smaller end of curve 1020. At the other end of thecoupling, in the opposite direction away from deflection, the opposingsegment 1030 will move along the curve 1020 away from the vertex.Segments mounted around the gasket 1015 at intermediate locationsbetween segment 1025 and segment 1030 will follow an elliptical path.The outer surfaces of these intermediate segments will maintain contactwith the concave inner surface 1020 of bell 1010 due to the continuouslychanging shape of inner surface 1020. The interface between theparabolic shapes of curve 1020 and the outer surface of segment 1025allow uniform loading of gasket 1015 and consistent engagement ofsegments 1025 throughout the joint. The major axis of the ellipticalpath can be defined by h=tangent (θ) times the effective diameter asmeasured across the outside surface of opposing segments. In thepreferred embodiment, θ is less than or equal to 15°. More preferably θis less than or equal to 10°; however, θ can be another angle.

In the preferred embodiment, when the joint is deflected, the outersurface of locking segment 125 follows a curve described by an ellipsein a plane inclined to the axis of the spigot. Each half of the ellipseon either side of the minor axis is a curve close enough in shape to aparabola so that the ellipse conforms closely to the paraboloid of bell110 as the joint is deflected.

In the preferred embodiment, the inner surface 235 of bell 110 and theouter surface 405 of segment 125 follow the shape of truncatedparaboloids, one positioned inside the other. The two paraboloids areaxially aligned when the joint is in the undeflected position.

In the preferred embodiment, no lubrication between spigot 105 andsealing device 115 is required. However, in other embodiments,lubricants can be applied to the inner surface of sealing device 115,the outer surface of spigot 110, or both. Preferably the lubricant is adry film lubricant. The lubricant can ease in assembly and/or providecorrosion protection to sealing device 115. Preferably, only a minimumamount (below industry standards) of lubricant is used.

The following examples illustrate embodiments of the current disclosurebut should not be viewed as limiting the scope of any claims flowingtherefrom.

Example

An experiment using two lengths of 8 inch pipe was conducted. One pipehad a bell as described herein while the other had a spigot as describedherein. The two lengths were joined using a sealing device as describedherein. The pipes were sealed at their respective open ends and theinternal cavity was pressurized. The experiment was conducted first withthe pipes having no deflection and then with the pipes having 5.7° ofdeflection. The results are compiled in Table 1.

Pressure Joint at Test No. of Deflection, Minimum Failure, FailureNumber Segments ° Pressure, psi psi Mode 1 8 0 700 772 Gasket Tear 2 8 0700 771 Gasket Tear 3 14 0 700 1192 Gasket Tear 4 10 0 700 998.5 GasketTear 5 10 5.7 700 828.2 Gasket Tear 6 14 7.50 700 1028 Gasket Tear

If “θ” is defined as the angle of deflection between the axis of thebell socket 1010 and the spigot 1005, through moderate angles ofdeflection, the locking segments 1025 following the major axis of anellipse projected onto a plane inclined perpendicular to the axis will,on the side of the complementary angle (180°−θ) be positioned nearer thevertex of the paraboloid of the bell socket 1010, and those on thecorresponding angle of deflection, θ, corresponding to the longer sideof the major axis of the ellipse will follow the curve of the paraboloidand be positioned further out on the major axis, but still in closeproximity to the bell socket 1010. Thus the elliptical path of thedeflected segments 1025 rotating within the paraboloid helps maintainproximity between the paraboloid outside surfaces of the lockingsegments 1025 and the paraboloid surface of the bell socket 1010 throughmoderate angles of deflection within the limits of the joint. At thecenter of rotation (during deflection), the segments 1025 are notdisplaced much beyond that of their original position on the circleperpendicular to the axis of the spigot 1005. The displacement ortranslation of the segments 1025 includes the ability to rotate into anoff-axis position to improve the engagement with a misaligned spigot1005 and to provide equalization of pressure between the bell curve andthe spigot end through the segments 1025. Thus, the engagement patternof the segments 1025 is approximately balanced around the spigot 1005whether deflected or not through moderate angles of deflection of thejoint.

The validity of this assertion can be seen by the engagement pattern ofsegment teeth of a gasket on a pipe spigot 1005 as shown in FIGS. 11-13for a joint that was deflected 5.7°, and pressurized to 828.2-psi beforethe gasket body ruptured. It can be seen that the engagement patternfollows an elliptical path about the pipe spigot 1005, and the depth ofpenetration of the teeth are very close, indicating relatively equalpressures between the bell socket 1010, segments 1025, and spigot 1005,even though the joint is deflected. Furthermore, segments rotated up toand beyond 30° during deflection. The joint in the photographs withstooda pressure of 828.2-psi before failure of the prototype gasket made of acatalyst-activated polyurethane. A molded SBR or EPDM vulcanized rubberwould be considerably stronger and would be expected to withstandgreater pressure before failure. Even thought the gasket rubber failed,the joint maintained engagement and did not separate. In each of thetests, the joints did not separate; all failures were due to theweakness of the castable urethane of the lab prototype gaskets.

Illustrated in FIG. 14 is an embodiment of an annular elastomeric gasketassembly 1100. The gasket assembly 1100 has an annular body 1101 havingan outer section 1103 with at least one groove 1105 in the outercircumference of the outer section 1103. Coupled to the outer section1103 are a plurality of substantially rigid members 1107.

FIG. 15 illustrates the components of a system 1114 for sealing a spigotand a bell, including the bell 1115, the gasket 1117, and the spigot1119. As stated with regard to the previous embodiment the gasket 1117is seated into the inner portion of the bell 1115 in the mannerpreviously described.

Illustrated in FIG. 16 is a cross-section of an embodiment of a gasket1120. A gasket 1120 has a first section 1121 and a second section 1123,the first section 1121 being axially adjacent to the second section1123. The gasket 1120 also has a front edge 1660. The first section 1121is between the front edge 1660 and the second section 1123. Illustratedin FIG. 16 are two grooves 1125 and 1127. Attached to the front of thegasket 1120 is a substantially rigid member 1129 attached to the frontedge 1660. The substantially rigid member includes a pair of teeth 1670extending radially inward, though any number of teeth may be present invarious embodiments. The first section 1121 of the gasket 1120 includesan upper surface 1640 and an inner surface 1650. The two grooves1125,1127 are defined in the upper surface 1640 and, in the currentembodiment, are V-shaped. The upper surface 1640 faces radially outwardand the inner surface 1650 faces radially inward. The second section1123 defines a gasket heel 1128, the gasket heel 1128 defining a heelsurface 1607, a first shoulder surface 1610, and a second shouldersurface 1620 distal from the first shoulder surface 1610. The secondsection also defines an annulus pocket 1630. In the current embodiment,the first shoulder surface 1610 and the second shoulder surface 1620extend radially inward from the heel surface 1607. The first shouldersurface 1610 extends from the heel surface 1607 towards the annuluspocket 1630, and the second shoulder surface 1620 extends from the heelsurface 1607 towards the upper surface 1640. In the current embodiment,the first shoulder surface 1610 and the second shoulder surface 1620 areorthogonal to the heel surface 1607. The upper surface 1640 extends fromthe front edge 1660 to the second shoulder surface 1620, and the innersurface 1650 extends from the front edge 1660 to the second section1123. The heel surface 1607 faces radially outward and iscylindrically-shaped. Further, in the current embodiment, the heelsurface 1607 is radially outward from the upper surface 1607.

The purpose of the grooves 1125 and 1127 are to allow the first section1121 to flex, thereby allowing the displacement of the front edge of thefirst section to be displaced in an axial and radial direction when thespigot 1005 is inserted. This displacement allows the substantiallyrigid member 1129 to move along the inner surface of the bell 1010 (i.e.out of the way of the outer surface of the spigot 1005) so as to reducethe friction generated between the substantially rigid member 1129 andthe spigot 1005. Other ways of enabling the incurvation of the firstsection 1121 of the gasket 1120 may be used. For example, the firstsection 1121 may be made of a more flexible material than the secondsection 1123. The first section 1121 and the second section 1123 may beseparate pieces coupled together in a flexible manner. Alternately, thefirst section 1121 may be provided with holes in the interior of thefirst section 1121, as a means of incurvating the first section 1121.

The substantially rigid members 1129 transfer the forces generated bythe friction of the insertion of the spigot 1005 to the first section1121 of the gasket 1120. The substantially rigid members 1129 may beprovided with geometry for gripping the outer surface of the spigot1005, such as the teeth 1131 illustrated in FIG. 16. Other geometriesfor gripping the outer surface of the spigot may include, for example,rough surfaces, a plurality of raised protrusions, and the like.

One of the advantages of the inner shape of the bell of the currentembodiment is that it allows for the use of single durometer material.Joint seals for ductile-iron pipe must accommodate a wide range ofvariations in the dimensions of the bells and spigots. Axial loading ofthe gaskets are a result of assembly forces and hydrostatic forces fromthe interior and exterior of the piping system. Typically, the softerrubbers used for effective sealing require longitudinal support toprevent displacing the seal during assembly and hydraulic loading.Commonly used joints require longitudinal support for the gasket byproviding a harder rubber anchored in a groove in the bell.

It has been determined that a single durometer gasket having a designlike the one illustrated as 115 in FIG. 1 may be deformed (roll over)under certain high pressure and/or high deflection conditions. In anembodiment of the current disclosure, illustrated in FIG. 17, a bell 110is illustrated with a gasket seating area 1151. In this embodiment theshape of the gasket seating area 1151 in combination with the shape ofthe gasket heel 1128 (in FIG. 17) serves to prevent rollover of a singledurometer gasket 1120 under higher pressure or high deflectionconditions. In this embodiment, as with the embodiment illustrated inFIG. 7, the incoming spigot 105 first passes past the segments 1129 andadvances to the K-type seal in the second section 1123 of the gasket1120. The combination of the gasket 1120 and the segment 1129 aredesigned to provide an interference fit between the spigot 105 and thesegments 1129 of approximately 0.010″. The elasticity of the gasket1120, the expanding diameter of the internal inner surface 235 of thebell 110, the design of segment 1129, and the expansion and contractiongrooves 1125 and 1127 of the gasket (shown in FIG. 16) facilitate theease of moving the segments 1129 out of the way during spigot insertion.The seating of a single durometer gasket 1120 deeper in the bell in thegasket seating area 1151 easily accommodates these forces. As the spigot105 advances, it passes through the area of the gasket 1120 having thegasket heel 1128 in the gasket seating area 1151 before encountering theK-type seal. As the end of the spigot 105 passes through the seal, theseal is stretched radially and the K-type seal is displaced in thedirection of the travel of the incoming spigot. Movement of the gasketheel 1128 is prevented by the seating surface in the gasket seating area1151. As the line (pipe) is filled with fluid and hydraulic force isapplied to the single durometer soft rubber gasket 1120, there will be atendency for the gasket 1120 to be displaced. The advancement of thegasket 1120 is stopped by the segments 1129 spaced around thecircumference of gasket 1120. Spacing of the segments 1129 is dictatedin part by the requirement of providing support for the gasket andpreventing extrusion of the gasket through the space between the bell110 and the spigot 105.

The desired attributes of the restrained joint of each embodiment of thecurrent disclosure include low insertion force, improved deflectioncapabilities, and improved segment loading efficiencies. The lowinsertion force attribute is addressed by the novel design of the gasket1120. Deflection capability and segment loading attributes are addressedby the interior profile of the bell 110 the gasket seating area 1151 andwhere the segments 1129 contact the interior surface 235 under thevarious component dimensional variations and locations of spigot 105including angular deflection and radial offset.

One aspect of the current disclosure is the use of parabolic shaped ramp(inner surface 235). The shape of the inner surface 235 approximates thepattern of a circular shape rotated through a plane. It should berecognized that slightly different parabolic curves are generated bydeflecting spigots of minimum, nominal, and maximum diameters. Startingwith these curves and enhancing them with adjustments for dimensionalvariations in other components resulted in the sequence of surfacesblended together to form the interior profile of the ramp where thesegment traverse for the varying degrees of deflection. Thesemodifications provide enhanced deflection capability and segmentengagement efficiency around the circumference of the spigot. This hasbeen demonstrated by post testing observations and measurements ofsegment engagement patterns including depth of tooth penetration.

The advantage provided becomes apparent when comparing the deflectioncapabilities and segment loading patterns of a bell 110 having anparaboloid inner surface 235 with a bell having a straight-line conicalsection inner surface which is used in prior art with wedge-actionlocking segments. In a bell with a straight-line conical section innersurface, without deflection of the spigot 105, one would see uniformloading around the circumference of the spigot 105 assuming that thebell and spigot are round. However, as the joint is deflected theloading on the individual segments would change as the spigot appliesadditional force on the segments toward the radius of deflection andreduces the force on the segments on the side away from the radius ofdeflection. This change in loading of the segments results in somesegments carrying a disproportional high load and other segmentscarrying much lower loads. This uneven loading pattern would putundesirable concentrated loading on the spigot which would be especiallycritical in spigots with thin walls. To some extent the negative impactof this uneven loading could be reduced by adding more segments but thatwould be an uneconomical solution and would not fully address theproblem.

Other inner surface shapes may be used with some sacrifice of loss ofsegment loading efficiency. In other words, as one moves from thepreferred embodiment through a series of concave shapes eventuallyending on a straight line (conical shape) the loading pattern (i.e. theforce required to insert the spigot 105) deteriorates. Practicallyspeaking though, a short series of conical sections that approximate thecurve of the preferred embodiment could produce less effective yetacceptable segment loading. Other concave shapes for inner surface 235with the shortest radii at the front of the bell would also work but,again, with some loss in segment loading efficiency.

Gripping the surface of a softer, lower tensile strength material suchas PVC typically requires substantially more contact area than forharder, higher tensile strength materials such as ductile iron. Thisincrease in contact area may be accomplished by maximizingcircumferential engagement and extending the length of linearengagement.

The number, spacing, and depth of serrations or teeth of segment 1129engaging the surface of spigot 105 must reflect the loading anticipatedon the restrained joint. The smaller tolerance on PVC pipe outsidediameters may require small modifications in the size of segment 1129and gasket profile. Lengthening of the segment 1129 to attain morelinear engagement would require more axial length of the inner surface235 (segment contact area) if the joint deflection capability forductile pipe systems is required for PVC.

FIG. 18 shows a circumferential curve in the segment. Segments may becut out of a ring machined to the profile shown in the cross section inFIG. 19. The curvature in an upper surface 1155 of the segment 1129facilitates the ability of the segment 1129 to move within the innersurface 235 of bell socket 220 to accommodate variations in deflectionsand spigot dimensions. The radius of curvature of the upper surface 1155need not be an exact match to the inner surface 235. For example, thesame segment 1129 may be used for pipes with 4-inch through 12-inchdiameters. Segments 1129 may also be cast or formed to the dimensions.For example, the cross section could be produced in a drawing operation(straight). A forming operation could then be used to put a curve in thesegment stock. Then, a shearing operation would be used to cut the stockinto segments. The dimensions of the segment 1129 are such that therewill be a slight interference with the incoming spigot 105 (e.g.approximately 0.010 inch). This interference is planned to maintaincontact of the teeth of the segment with the outer surface of the spigot105 and to energize the first section 1121 of the gasket 1120, where thegasket 1120 is attached to the segment 1129.

Illustrated in FIG. 19 is a segment 1129 with two possible shapes forthe upper surface of segment 1129. The upper surface 1155 configuration(in dashed line) is a simple radius curve. An upper surfaceconfiguration 1156 may be provided to adjust for tolerances in thevarious joint components and for deflections of the spigot 105 in thebell 110. Similarly, the second tooth 1158 (dashed line) of segment 1129may be extended (illustrated as second tooth 1159 in a solid line) toadjust for such tolerances.

FIG. 20 shows an exploded cross section of the segment 1129 toillustrate four features on the upper surface 1155 of the segment 1129as well as the lowering of the second tooth. The first portion of theupper surface 1155 may be a straight line to increase contact in theforward portion of the inner surface 235 to keep the segment 1129 fromcoming out of the bell 110. In this embodiment, the straight section Adoes not match the curve in the inner surface 235 and the mismatchresults in interference with the front of the bell making furthermovement of the segment 1129 difficult. Portions B and C of the segment1129 illustrated in FIG. 20 may be curved surfaces designed to maximizesurface contact for variations in spigot diameters and deflections ofthe joint. The whole top of the segment and the bell contour is designedto maximize the axial loading component of the force vector. Portion Dis provided to maintain segment location during gasket production.Portion D prevents the bending in the cylindrical portion of the gasketthat causes the segment to rotate (clockwise) out of position. Rotationof the segment out of position could lead to improper tooth engagement.This design helps to maintain contact of both teeth on the spigotsurface. In addition, the design eliminates the possibility of a sharpupper back corner of the segment engaging with the surface of the belland causing a counter clockwise rotation of the segment causing damageto the gasket. To avoid having a situation where only the first toothengages the spigot in certain specific joint configurations, the secondtooth may be extended (portion E) so that both teeth remain in contactwith the spigot. Single tooth engagement brings increased risk of spigotpenetration, tooth breakage, or lack of engagement. In the preferredembodiment, the included angle in the first tooth 1157 is approximately60° and the included angle in the second tooth 1159 is approximately54°.

Locking segments 1129 have more freedom of movement (axially, radially,and rotating off-axis circumferentially). Segments currently in use aretypically constrained axially by a retainer bead and a retainer seat ofexisting bell sockets, and laterally by the hard and soft rubber of thegasket (dual durometer) which hold them in position and separate andspace them. These segments are free to pivot within the bell about theretainer bead for 4″ through 24″ sizes, and within a retainer groove for30″ and 36″ sizes. The pivoting action is restricted to a path that isaxially aligned with the centerline of the mating pipes. Consequently,the teeth of segments currently in use will, under proper assemblyconditions, engage the spigot of the mating pipe in a circumferentialpattern. Also, the segments currently in use are constrained radially bythe height of the annulus between the bell socket and the mating spigot.Out-of-round conditions can impair performance beyond the ability of thesegments to compensate by moving axially within the bell socket.

The segments 1129 are not securely locked in position since they aremounted by attachment of the back edge of the back tooth 1159 of thesegment to the front edge of the gasket 1120. The segments do not haveto be encapsulated in the gasket 1120. Because the gasket 1120 is anelastic material capable of considerable deformation, the segments 1129can rotate off-axis, and also move axially within reasonable limitsbeyond the normal confines of the segment upper surface 1155 tocompensate for out-of-roundness or other irregularities in bell socket220 or spigot 105.

The cross sectional shape of the gasket 1120 in FIG. 16 also facilitatesfreedom of movement of the segments by the inclusion of carefullyselected angles of the gasket edge and back edge of the segments 1129where they mount to the gasket. The inclusion of expansion/contractiongrooves 1125 and 1127 (shown in FIG. 16) in the gasket end behind thesegment 1129 allow additional freedom of movement of the segments withthe curve of inner surface 235 of bell socket 220. The segments 1129have radial freedom of movement to conform to the inner surface 235 ofbell socket 220 by ramping up toward the vertex of the paraboloid as themating spigot is withdrawn.

Another feature is that once the teeth 1157 and 1159 of the segment 1129are locked in position in the surface of the spigot 105 by penetration,additional deflection is still available in the joint by flexure of thealigned segments as a whole. Thus the engaged joint is not rigid as withcurrently used joints but permits some flexure resembling ball jointaction. This feature may make the joint suitable for additionalapplications such as HDD (Horizontal Direction Drilling).

For ductile iron pipe components, the segments 1129 may be manufacturedfrom suitable steel capable of being heat treated to adequate hardnessand other key physical properties by any of several methods. The formingmethods include machining a ring with the curved bearing surface of thesegment on the outside diameter, the teeth on the inside diameter, andsuitably machined nose and back tooth angles. Segments of suitablelength can then be cut radially from the ring and heat treated.

The segments 1129 may be made from steel bar stock cold-drawn as astraight bar with the suitable profile, cut into lengths long enough toroll-form into a semicircle, and then further cut into segments ofsuitable length prior to heat treating. Alternately, the segments 1129may be produced by investment casting provided the foundry and itstoolmaker have the technology to maintain all critical profiles anddetails, including tooth sharpness and freedom from porosity.

Segments 1129 for plastic pipe, such as PVC, may be machined from hardplastic stock or metal as described above, or may be molded from aharder plastic such as polycarbonate or ABS by heating and injectinginto a suitable metal die cavity. The principal material requirementhere is that the segment material be harder and stronger that the PVCpipe, be capable of supporting relatively sharp teeth, and be economicalsince the circumferential and axial engagement pattern must besubstantially greater than that for ductile iron. If metal segments arechosen, it is unlikely that hardening by heat treating will be required.

The gasket body 1120 will be more economical to produce since singledurometer rubber will be used as opposed to dual hardness rubber forpresently used gaskets. Also, the gasket 1120 may be thinner thanpresently used gaskets making it lighter and requiring less material.Curing times should be permissive of shorter mold curing cycles,increasing machine output.

The bite pattern on spigots pressure tested with gaskets made inaccordance with the current disclosure (see FIGS. 11-13) demonstratesthe unique ability of the individual segments 1129 to seek a locationthat maximizes their engagement with the spigot 105. The bite marks shownot only the location of the each segment 1129 but also theirorientations and the depths of penetration of the teeth. Studies ofpost-testing spigots show that segments have the flexibility to moveaxially and rotate off-axis. Tooth penetration, including the two teethof individual segments, was uniform around the periphery of the spigot.

It has also been observed that after pressure testing assemblies indeflected positions, the angle of deflection of the joint could easilybe changed. Subsequent evaluations indicated that the segments (withtheir teeth imbedded in the spigot surface) and the spigot moved as aunit within the inner curvatures of the bell.

The uniformity in depths of bite marks shows even distribution of theload around the spigot 105. This is particularly advantageous as themetal thicknesses of pipe walls are reduced. The ability of the joint todeflect after the teeth have set is a favorable contrast to jointspresently in use that are essentially rigid after being pressurized.

The freedom of movement of the locking segments 1129, including movementout of the path of the incoming spigot 105, is one advantage. Whileminimizing the drag on the spigot, the compressed elastomer maintains anaxial force on the segment so that it fills the available and possiblychanging gap. This auto-positioning of the individual segments 1129keeps them in contact with the surface of the spigot 105. When thespigot 105 starts to retract the segments engage quickly, minimizing theamount of joint pull out during pressurization.

Another embodiment of the system is seen in FIG. 21. System 2100includes a spigot 2105, a bell 2110, and a sealing device which, in thecurrent embodiment, is shown as gasket 1120′, which is an annularelastomeric member in the current embodiment. Additionally,substantially rigid member 1129 is shown along with the system 2100.Several features of this embodiment are highlighted below.

Testing of prior embodiments showed that, at maximum deflection anglesand extremely high pressures—including pressures far above typicaloperation limits, for example, 1000 psi—a small portion of the gasketcould extrude and be seen at the face of the bell 110 ofpreviously-described embodiments. While this did not necessarily impedeperformance, concerns were raised about the durability of such aconfiguration in long-term operation. The problem was eliminated as seenin the embodiment of FIGS. 21 and 22. An extended lip 2151 to the gasketseating area 1151 in the bell 2110 anchors the gasket 1120′. Theextended lip 2151 extends radially into the bell 2110 further than inprior embodiments. Because the extended lip 2151 retains a gasket heel1128 of the gasket 1120′, the gasket 1120′ is unable to extrude beyondthe extended lip 2151 without significant malformation, a condition thatis not possible in this configuration.

Additionally, an insertion groove 2152 is shown added ahead of thegasket heel 1128 of the gasket 1120′. The insertion groove 2152 allowsthe gasket 1120′ of the current embodiment to seat more easily in thealtered profile created by the extended lip 2151, as previouslydescribed. The insertion groove 2152 is shown oriented radially on thegasket heel 1128 to interface with the extended lip 2151. The insertiongroove 2152 allows a mating relationship with the extended lip 2151 thatfurther prevents rollout of the gasket 1120′ under pressure.

In the current embodiment, an inner surface 2235 of the bell 2110defines a blended curve that includes several portions. In the currentembodiment, each portion is a paraboloid portion, including a firstportion 2236 which is a large paraboloid and a second portion 2238 whichis a smaller paraboloid. As such, the truncated elliptic paraboloid ofother embodiments may include two paraboloid portions as described withreference to the current embodiment. Because the paraboloids of thefirst portion 2236 and the second portion 2238 form a blended curve, theinner surface 2235 of the bell 2110 is not easily described throughmathematical formulae. A conical portion may be included between thefirst portion 2236 and the second portion 2238 in some embodiments. Theconical portion allows for tolerancing to blend the first portion 2236with the second portion 2238. For the sake of understanding the currentembodiment, the paraboloid portions may be characterized as having aradii of curvature that approximates a parabolic shape in the regionspecified. In the current embodiment, the first portion 2236 may beroughly approximated by a surface having a radius of curvature of about⅔ the pipe diameter; the second portion 2238 may be roughly approximatedby a surface having a radius of curvature of about ⅓ the pipe diameter.The first portion 2236 of the inner surface 2235 is continuous frompoint 2241 to point 2242 in the current embodiment. The second portion2238 is continuous from point 2242 to point 2243 in the currentembodiment. For reference, the pipe diameter of the current embodimentis 6 inches.

Although the radii of curvature of various portions are shown anddescribed in relation to the pipe diameter of the current embodiment,one of skill in the art would understand that the radius of curvature ofparticular portions may or may not change in other embodiments. Forexample, joints with larger or smaller pipe diameters in someembodiments may include a first portion having a radius of curvature of⅔ the pipe diameter and a second portion having a radius of curvature of⅓ the pipe diameter. In other embodiments, joints with larger or smallerpipe diameters may include the same surface profile in the samedimensions shown and described herein, regardless of the diameter of thepipe.

The inner surface 2235 of the current embodiment provides severaladvantages over previously-described embodiments. First, it allowsgreater engagement of the substantially rigid members 1129 with theinner surface 2235 of the bell 2110 during deflection of a joint madebetween the bell 2110 and the spigot 2105. As the joint deflects and thebell 2110 and spigot 2105 become angled with respect to each other, thepoint of each substantially rigid member 1129 that contacts the innersurface 2235 may change. Because deflection of the joint will cause thesubstantially rigid members 1129 to travel along the curvature of theinner surface 2235, the blended curve arrangement of the inner surface2235 accounts for the contact point of the substantially rigid members1129 with the inner surface 2235 to change as the joint deflects. Assuch, even though each substantially rigid member 1129 may be movingalong the inner surface 2235 and rotating to maintain engagement withthe spigot 2105, the blended curve profile of the inner surface 2235ensures that each substantially rigid member 1129 maintains contact withthe inner surface 2235, thereby promoting the engagement of eachsubstantially rigid member 1129 with the spigot 2105.

Moreover, the blended curve arrangement of the inner surface 2235 takesbetter account of pipe tolerances to allow better engagement by thesubstantially rigid members 1129 when the spigot 2105 and bell 2110 areat maximum or minimum manufacturing tolerances. An incurving portion2289 is also seen leading to the extended lip 2151. In the currentembodiment, the incurving portion 2289 is included to allow a flow pathfor casting the extended lip 2151. Other advantages may be seen intolerancing as well as function.

In prior embodiments, a bell throat 225 is shown as a positive stop,wherein the ledge of the bell throat 225 is oriented radially. Thisarrangement can provide a challenge during casting of the bell 210.

In the current embodiment, a nose curve portion 2249 is used to providea stop for translational movement of the substantially rigid members1129 in biting engagement with the spigot 2105. Although priorembodiments displayed the bell throat 225 as a positive stop, such anarrangement is not necessary. As such, the nose curve portion 2249 ofthe current embodiment does not require special casting elements and canbe cast more easily than previously-described embodiments whileproviding similar functionality.

It should also be noted that an elliptical portion 2107 can be seenalong an end 2106 of the spigot 2105 in the current embodiment. A radialdimension of the elliptical portion 2107 covers about one-half of thewall thickness of the spigot 2105. An axial dimension of the ellipticalportion 2107 is about three times as large as the radial dimension.Together, the elliptical portion 2107 defines one quarter of an ellipse.The elliptical portion 2107 aids in the deflection of the joint bypreventing the end 2106 of the spigot 2105 from restricting additionaldeflection. In most applications, a bevel (shown in FIGS. 11-13) isadded to the end of spigot 105 before the spigot 105 is inserted intothe bell 110. The elliptical portion 2107 of spigot 2105 may be castinstead of being added in the field, thereby preventing a fieldtechnician from taking the additional step of adding the bevel.

Other embodiments and uses will be apparent to those skilled in the artfrom consideration of the specification and practice of the embodimentsdisclosed herein. All references cited herein, including allpublications, U.S. and foreign patents and patent applications, arespecifically and entirely incorporated by reference. It is intended thatthe specification and examples be considered exemplary only with thetrue scope and spirit of the disclosure indicated by the followingclaims. Furthermore, the term “comprising” includes the terms“consisting of” and “consisting essentially of,” and the termscomprising, including, and containing are not intended to be limiting.

1. A system for sealing a spigot, the system comprising: a gasket, thegasket having a front end, a first section, and a second section, thegasket defining at least one groove in the first section; at least onesubstantially rigid member contacting the front end, the substantiallyrigid member made of a material that is more rigid than a material ofthe gasket; and a bell encircling the gasket, the bell defining a gasketseating area, the bell including an inner surface, wherein the innersurface includes a blended curve and directly contacts the at least onesubstantially rigid member.
 2. The system of claim 1, wherein the gasketdefines an insertion groove.
 3. The system of claim 2, wherein theinsertion groove is defined at the joining point of the first sectionand the second section.
 4. The system of claim 2, wherein the insertiongroove mates with an extended lip of the bell.
 5. The system of claim 1,wherein the bell includes an extended lip.
 6. The system of claim 5,wherein the extended lip is proximate the gasket seating area.
 7. Thesystem of claim 1, wherein the gasket includes a gasket heel, andwherein the gasket heel mates with the gasket seating area.
 8. Thesystem of claim 1, wherein the substantially rigid member includesteeth.
 9. The system of claim 1, wherein the spigot includes an end andwherein the end includes a quarter ellipse portion.
 10. A method ofcreating and maintaining a sealed interface between a spigot and a bell,the method comprising: obtaining an annular elastomeric member having afront edge, a first section, and a second section, the annularelastomeric member defining at least one expansion and contractiongroove and an insertion groove, the at least one expansion andcontraction groove defining an open space within the at least oneexpansion and contraction groove; seating the second section of theannular elastomeric member in a gasket seating area of the bell, thegasket seating area including an extended lip; displacing the firstsection of the annular elastomeric member in at least one of an axialand a radial direction in response to forces generated by the insertionof the spigot; and securing the first section of the annular elastomericmember to the spigot.
 11. The method of claim 10, wherein the bellincludes an inner surface, the inner surface defining a blended curve,the blended curve including at least one paraboloid.
 12. The method ofclaim 10 wherein the step of displacing the first section of the annularelastomeric member comprises incurvating the first section of theannular elastomeric member; whereby the front edge is displaced axiallyby the insertion of the spigot.
 13. The method of claim 10 furthercomprising creating an annulus pocket and lip seal between the spigotand the bell with the second section of the annular elastomeric member.14. The method of claim 10 wherein the annular elastomeric member has aplurality of substantially rigid members disposed on the front edge ofthe annular elastomeric member, whereby the axial forces generated bythe insertion of spigot are transferred to the substantially rigidmembers and thereby to the front edge of the annular elastomeric memberthereby causing the first section of the annular elastomeric member tobe displaced in an axial and radial direction.
 15. The method of claim14 wherein the method element of securing the first section of theannular elastomeric member to the spigot includes gripping the spigotwith the substantially rigid members.
 16. The method of claim 15 furthercomprising slightly displacing the spigot away from the bell.
 17. Asystem for sealing a spigot, the system comprising: a gasket, the gaskethaving a front end, a first section, and a second section, the gasketdefining at least one groove and at least one insertion groove; at leastone substantially rigid member contacting the front end, thesubstantially rigid member made of a material that is more rigid than amaterial of the gasket; and a bell encircling the gasket, the belldefining a gasket seating area including an extended lip, the bellincluding an inner surface, the inner surface defining a blended curve,the blended curve including at least one paraboloid; wherein theextended lip and the insertion groove are arranged in matingrelationship.
 18. The system of claim 17, wherein the insertion grooveis defined at the joining point of the first section and the secondsection.
 19. The system of claim 17, wherein the spigot includes an endand wherein the end includes a quarter ellipse portion.
 20. The systemof claim 17, wherein the at least one groove is defined in an uppersurface of the first section, the upper surface facing radially outward.21. An annular elastomeric gasket comprising: a front end; a firstsection, the first section including an upper surface facing radiallyoutward, an inner surface facing radially inward, and at least onegroove; a second section axially adjacent to the first section, thesecond section including a lip seal and a gasket heel, the gasket heeldefining a radially outermost top surface; and a bulb-shaped portion,the bulb-shaped portion formed between the front end and the firstsection, the bulb-shaped portion including an upper bulb surface and aninner bulb surface, a bulb thickness of the bulb-shaped portion largerthan a first section thickness of the first section, the upper bulbsurface radially inward from the radially outermost top surface of thegasket heel.
 22. The gasket of claim 21, wherein the upper bulb surfaceof the bulb-shaped portion includes a radially outermost point radiallyoutward from a radially outermost point of the upper surface of thefirst section.
 23. The gasket of claim 21, wherein the bulb-shapedportion includes a lower curved surface, the lower curved surface havinga radially innermost point radially inward from a radially outermostpoint of the inner surface of the first section.
 24. The gasket of claim21, wherein the bulb-shaped portion defines a taper tapering towards thefront end.
 25. The gasket of claim 21, wherein the at least one grooveis two grooves.
 26. The gasket of claim 21, wherein the at least onegroove is defined in the upper surface.
 27. The gasket of claim 21,wherein the annular elastomeric gasket is formed from a single material.